Wikipedia's definition of life hack is simple and effective:
Life hack (or life hacking) refers to any trick, shortcut, skill, or novelty method that increases productivity and efficiency, in all walks of life. The term was primarily used by computer experts who suffer from information overload or those with a playful curiosity in the ways they can accelerate their workflow in ways other than programming.
When everything is a life hack, or a hack of some type, the phrase loses all meaning.
"Life hacks... [for] 2016" include gems like "Make a healthy and filling breakfast". Precisely how making breakfast hacks anything, or why 2016 is the time to start making it, is left unexplained.
"Job search hacks" would make sense if they were, say, cover letter templates. "Be a storyteller", though? That's a tip on presentation, not on productivity or efficiency.
"Romance hacks" appear to be (usually) decent relationship advice clouded in verbiage that make them sound like used car promotions. Phrases like "With this, she knows you care but more importantly, she knows you LISTEN." and "Honestly, I've met men that were ripe for the picking because their wives/girlfriends didn't show any appreciation or seem to value them at all" make me scratch my head.
As if the proliferation of life hacks hadn't yet jumped the shark, "walking hacks" include advice like "Walk when it is cooler" and "Bring water". When bringing water on a summer walk is a hack, what isn't? (That said, the article did teach me that June is Great Outdoors Month. Guess I'll go for a walk soon.)
Much like the flogging the poor word "leverage" endured in the '90s and '00s, "hack" is becoming so ubiquitous it's losing its original meaning. If Jessica Stillman writes a 2017 companion article to the her article I linked in the previous sentence ("8 Phrases You Really Need to Stop Saying in 2016"), I sure hope "hack" finds its way there.
For those more inclined toward the technical side of things, including a healthy dose of the meaning of hacking itself, Gizmodo's article from a couple years ago does a good job. My examples were published since that article came out. Consider this entry Anti-Hacking for Business Students.